The invention relates to a bending device for bending plastically deformable strip material, having an advance unit, a guide unit and a bending unit, where the bending unit has a bending roller and a reverse bending unit.
This bending unit is known from DE-OS 198 16 609 A1. It is used for bending sections of strip material which can be used to produce flat-blade windshield wipers. The bending unit of this known bending device consists essentially of several locating points through which the strip material to be bent is guided. Depending on the desired bending radius, the relative position of the locating points to each other is changed. In order to obtain high-precision bent parts, it is necessary to reduce the residual stress created in the strip material during bending by controlled reverse bending and thus ensure the formal accuracy of the work piece during operation. The reverse bending unit of the known bending unit consists essentially of a bending roller whose relative position to the bending unit can be altered, so that reverse bending can be adjusted to the desired degree.
The disadvantage of this bending device is that the position of the reverse bending unit depends both on the position of the bending unit as well as on the desired degree of reverse bending. The consequence of the dependence of the position of the reverse bending unit on the bending unit is that, even with constant reverse bending but changing initial bending, the reverse bending unit has to be controlled to match the change in the bend. If both bending and reverse bending are to be changed during the bending process, both the above dependencies have to be taken into consideration when controlling the position of the reverse bending unit. Coupling the bending and reverse bending processes can have negative effects on the quality of the work pieces and in addition requires great expense on the machine and the control side.
The object of the invention is to prepare a bending device for bending plastically deformable strip material with which the work pieces can be produced to the highest quality and which is nevertheless simply constructed and simple to control.
This object is achieved under the invention by a bending device for bending plastically deformable strip material, having an advance unit, a guide unit, a bending unit with a reverse bending unit, where the relative position of the reverse bending unit to the bending unit is adjustable and where the reverse bending unit is mounted moveably on the bending unit.
As a result of the inventive positioning of the reverse bending unit on the bending unit, it is possible to keep the reverse bending, or the reverse bending torque, respectively, constant when the bend is changed during the bending process with little expense for control equipment, since the reverse bending unit also performs the adjusting movements for the bending unit. If the reverse bend is to be changed during the bending process, it is only necessary to move the reverse bending unit relative to the bending unit, so that compared with the known bending unit a decoupled, simpler and more precise control of the reverse bending unit is achieved.
In one version of the bending unit under the invention, provision is made for the bending unit to have a bending roller and for the reverse bending unit to be rotatable about the axis of rotation of the bending roller, so that the reverse bending unit is mounted to the bending unit with a simple, economical and accurate pivot bearing.
To improve the invention the bending unit can be moved slidingly relative to the guide unit, so that different bending radii are possible.
In one aspect of the invention the position of the bending unit is controlled relative to the guide unit, specifically numerically controlled, so that a change in the bending radius is possible during the bending process.
In another aspect of the invention the rotation of the reverse bending unit around the axis of rotation of the bending roller is controlled, specifically numerically controlled, so that the reverse bend can also be changed during the bending process.
In an improvement of the invention, the reverse bending unit has a crank on which a reverse bending roller is located, resulting in simple construction of the inventive bending device, capable of sustaining a high mechanical load.
In a further improvement of the invention, the distance of the reverse bending roller to the axis of rotation of the bending roller is adjustable so that a further degree of freedom is attained in shaping of the reverse bending process.
In other aspects of the invention provision is made for an actuator to rotate the reverse bending unit at least indirectly, specifically for a pneumatic cylinder, a hydraulic cylinder, a linear motor or a servo motor, to be provided so that the reverse bending unit can be rotated depending on the required accuracy of positioning.
In one aspect of the invention a pinion is furnished on the reverse bending unit, whose center lies in the axis of rotation of the bending roller and the actuator drives a rack interacting with the pinion so that, independently of the rotational position of the reverse bending unit, the force of the actuator is proportional to the torque exerted by the reverse bending on the strip material. A constant reverse bending torque can thereby be set in a very simple way.
In another aspect of the invention the actuator is articulated at a point outside the rotational axis of the bending roller on the reverse bending unit so that control of the reverse bending unit is simple and economical.
Another aspect envisions that a servo drive is provided as the actuator.
In one aspect of the invention the guide unit has several guide rollers positioned on both sides of the strip materials so that aligning and guiding the strip material involves low-friction and is economical and operationally safe.
As an improvement to the invention provision is made for the advance unit to have at least two advance rollers positioned on opposite sides of the strip material and for at least one advance roller to be driven by a motor, so that the strip material can be transported through the bending unit in a simple way. The drive for the advance unit can be numerically controlled.
In a further improvement to the invention, provision is made for a cutting unit, also numerically controlled, so that after a workpiece is completed it can be separated from the strip material.
In a further improvement of the invention, a reader is furnished which sends signals to the bending device controls depending on markings on the strip material so that no serial failures occur in the production of work pieces from the strip material.